1. Field of the Invention
The present invention relates to a semiconductor memory device. More particularly, it relates to a semiconductor memory device providing high speed data transmission between memory cells.
2. Description of the Related Art
In a semiconductor memory device including, for example, a plurality of dynamic type random access memory cells (RAM) each of which comprises a transfer gate transistor and a capacitor, data transmissions are performed between each of the memory cells to move an image on a display apparatus, for example, a cathode-ray tube display (CRT). This movement of the image is, in general, called "scrolling". In a "scrolling" action, the image is moved upward or downward on the display surface. This method is performed in such a way that, first, each word line of the dynamic type RAM corresponds to each horizontal scanning line of the CRT; second, in the case of upward "scrolling", the data of each memory cell connected to the second word line is transferred to each memory cell connected to the first word line, and the data of each memory cell connected to the third word line is transferred to each memory cell connected to the second word line. A similar operation is repeatedly performed to each memory cell connected for the final word line.
In the conventional method, however, it is difficult to achieve high speed "scrolling" because data transmission is sequentially performed for every memory cell. That is, first, data of one memory cell is read out; second, the read out data is written in an external register; third, the data in the external register is read out; and finally, the read out data is written in the other memory cell. These read out/write cycles are performed for each and every memory cell.
This problem will be explained in detail hereinafter.